Electroformed articles and process for their manufacture



Jan. 27, 1959 E. D. BOELTER, JR

ELECTROFORMED ARTICLES, AND PROCESS FOR THEIR MANUFACTURE Filed 001;.28, 1955 m w m um mm- .H 2 Ni P A .1 2 W l lfi HM h A mmm 1 .I/Hx I 1H EMi an Mn; \JWJW M I w i m M MD w w H H H m I E t I 11 g m ATTORN YUnited States Patent cc 2,870,709 ELECTROFORMED ARTICLES AND PROCESS F0THEIR MANUFACTURE Edwin D. Boelter, Jr., Niagara Falls, N. Y., assignorto E. I. du Pont de Nemours and Company, Wilmington,

Del., a corporation of Delaware Application October 28, 1955, Serial No.543,496 2 Claims. (Cl. 102-24) This application, a continuation-in-partof my copendmg application Serial Number 426,950, filed May 3, 1954, andnow abandoned, relates to electroformed copper articles and to a processfor preparing the same.

In the above-mentioned application there is claimed a process forelectrodepositing copper at unusually high current densities from asubstantially conventional aqueous copper cyanide bath modified by theinclusion therein of an inorganic selenide such'as sodium or copperselenide. The quantity of additive used is not sharply critical butshould comprise between about 50 and 1000 p. p. In. of the bath.

selenide bath at very high rates of speed, i. e., one mil 'per minute orgreater, in an extremely ductile form. This copper is free of internalstrain and can readily be deposited to any predetermined thickness onsurfaces having a low radius of curvature. If the surface is one towhich copper will adhere, such as carbon steel, the electrodeposit willbe held tenaciously. If, on the other hand, the surface is one to whichcopper will not adhere, such as polished chromium or stainless steel,the copper can easily be stripped therefrom retaining the shape of thebase.

Copper can thus be plated at high speeds from the novel baths onto amandrel and easily removed from the latter. Articles terminating in apoint or other closed base can, in particular, be formed as described.Such articles, which may be termed concave, include cones, cups, bowls,fountain-pen caps and the like.

i The cones of this invention have an entirely unexpected property whichmakes them of great value: they are extremely eifective as liners forsmall shaped charges.

When so adapted, they surprisingly increase the penetrating power of thecharges to a value about 12-15% greater than that obtained with linersmade by conventional methods such as deep-drawing or forming the copper.

These shaped charges are particularly valuable in devices such as jetperforators. Jet perforators are described in many publications as, forexample, the Muskat et a1. U. S. Patent 2,494,256. Used for piercing oilwell casings, they consist primarily of a small shaped charge of highexplosives held within a container, a mean for detonating the chargefrom one end and an internal metallic liner in the end opposite thepoint of detonation. When the charge is set off the conical linercollapses from apex to base and ejects a metallic stream of such highvelocity and small cross section that it readily penetrates anythingbefore it. The initiating means is usually a detonating fuse, but adetonator may be employed if desired.

A specific object of the invention is, therefore, provision of a methodfor making copper cones adapted for use in producing jet perforators.

Other objects will be apparent from the remainder of the specificationand from the drawings, in which:

Figure 1 shows an electroplating bath and apparatus for producing thecones of the invention; 7

. Figure 2 is a section of a jet perforator, positioned for use, showingthe electrodeposited conical liner; and

Figure 3 is an elevation of a jet perforator mounted on a pile of steelplates for testing perforation.

Figure 1 discloses tank 10 containing bath 12, shield It has now beenfound that copper will deposit from the 2,870,709 Patented Jan. 27, 195914, and anode 16. Rotating mandrel 18, partly insulated,- serves as thecathode. Pump 20 is provided to remove part of the bath from the lowerportion of the tank, pass it through filter 17, and impinge a spray 21onto the tip of the mandrel and the cone 30 being formed. Use of such aspray is almost essential to insure strength and uniformity of thedeposit at the closure when articles terminating in a point or roundedapex, as the preferred cones of the invention, are made.

The composition of andconditions for operating the bath of Figure 1 areessentially those of the copending application except for use of theliquid spray. The spray is maintained by the pump operated at a rateproportional to the desired plating speed. A spray velocity of about500-1000 ft./ minute is satisfactory for a plating speed of 1 mil/minute.

Usable bath compositions and conditions include:

Preferred conditions permitting use of current densities of about 850amperes per square foot or a plating speed of up to about one mil/minute are: Y

CuCN About 10 oz./gal.' Free KCN About 1 oz./ gal.

KOH About 1 oz./gal. Na Se About 200 p. p. 111. Temperature About -90 C.

Since the selenium is deposited with the copper to the extent of about2-300 p. p. m. the desired concentrations must be maintained byoccasional additions to the bath. These additions may be made, as maythe original, in the form of Cu Se if it is so desired. An organicanti-pitting agent such as methylene-bis(naphthalene sulfonic acid) inthe aor [3- form, C-decyl betaine or the like should also be used toimprove the copper deposits. The concentration of this agent may vary inthe bath from about to 500 p. p. m., about 200 p. p. 111. beingpreferred.

Other plating techniques may be used in operating the process of theinvention including current reversal and current interruption. Neitherof these current manipulations appreciably affects the properties of thepreferred cones of the invention.

As noted above, when cones prepared from a copper cyanide bathcontaining a selenide are utilized as the liner for the small shapedcharge of a jet perforator, they increase the penetrating power of thelatter about 12- 15%. This increase in penetrating power renders theperforators especially valuable for use in oil wells. Figure 2 shows ajet perforator 22 positioned :for use against oil well casing 23. Theperforator consists of container 24, initiating means 26, and shapedcharge 28. In the broad end of the shaped charge is inserted liner 30,preferably formed on the apparatus of Figure l.

Electrodeposited cones are of primary value at small sizes, i. e., up totwo inches in both diameter and height, and with small charges of 10-25g. of explosive. Both larger cones and larger charges can be usedalthough in such cases the improvement due to electrodeposition from theselenium-containing bath becomes more diificult to assess.

The reason for the enhanced penetrating power of shaped charges linedwith electroformed copper cones is not precisely known but is believeddue to the exact uniformity of the cone structure. The uniformity of thecone in thickness and around the center axis prevents collapse from anumber of centers and thus yields a reproeliminated only by polishingthe workpiece during interruption in the deposition. The mandrelemployed must be-adherent to the copper to retain the latter duringpolishing operations but also fusible so that it can eventually 'beseparated from the article produced. Copper prepared in this manner isnon-uniform and possessed of no unusual properties in regard to liningshaped charges. Conventional cyanide baths heretofore utilized employcurrent densities which are too low for electroforming.

There follow some examples serving to illustrate the practice of theinvention:

EXAMPLE 1 This example shows the penetrating power of jet perforatorslined with copper cones prepared on the apparatus of Figure 1.

Copper cones were electrodeposited from an aqueous cyanide bath upon apolished chromium mandrel under the following conditions:

CuCN "oz/gal-.. 15 Free KCN oz./gal- 1-2 KOH oz./gal 2 Na Se p. p. in...50200 Temperature 86 Rate of revolution of the mandrel R. P. M 600-2000Spray velocity ft./min 850-1000 Distance between jet outlet and tip ofmandrel inch 2, Current (D. C.) A./S. F 200-340 The cones weresubsequently directly stripped from the mandrel in a single operation.Each cone was 1 inch high externally, 1.31 inches in diameter at itsbase and possessed an angle of 60. The copper was electrodeposited to athickness of about 17-20 mils.

Into each cone was forced, at a pressure of 20,000

p. s. i., an 18 gram charge of cyclonite and wax having a weight ratioof 95:5. The resultant assembly was tested as shown in Figure 3, whichdisplays the jet perforator 22 positioned on a stack of steel plates 32each one inch in thickness. The perforator was detonated and the depthof penetration into the plates and the diameter of the hole formed weremeasured. Results are given in Table I.

Table l.--Penetration with electroformed cones Depth of Diameter ConePenetration, of Hole in inches 1st Plate,

inches were. rmmeorm 9999. UlOlkOUF A The tests recorded in Table I wererepeated with cones made utilizing both current reversal and currentinterruption. Results were the same with this second group of cones.

' 1 EXAMPLE 2 I example .shows the results of penetration tests withcones made from sheet copper and is included solely as a control,

The testsof Example'l were substantially. repeatedexr cept that thelining utilized were prepared by deep-drawing sheet copper. The.dimensions of the cones and the weights of the charges weresubstantially the same as in that example. Results are given in TableII.

Table II.-Penetratidn with drawn co nes Depth of Diameter of 1 ConePenetration, Hole in 1st inches Plate, inches Average 3. 91 0.

EXAMPLE 3 This example, also included as a control, shows the results ofpenetration tests with electroformed cones pre- 1 pared by prior, artelectroforming processes.

The tests of Example 1 were substantially repeated except that thelinings utilized were prepared by electroforming copper from aconventional bathcontaining no selenium. The dimensions of the cones andthe weights Having described my invention, I claim: 1. In a jetperforator comprising a shapcdcharge means for detonating said shapedcharge, a container sub stantially surrounding the shaped charge-and "acavity in the base of the same, a lining in said cavity comprising asubstantially strain-free copper cone producedby'eiectrodepositingcopper from an alkaline copper cyanide bath ing 50-1000 p. p. m. of aninorganic shelenide.

2. A liner for a shaped charge comprising a substantially strain-freecopper cone produced by electrodepositing copper from an alkaline coppercyanide bath eontaining 50 1000 p. p. m. of an inorganic selenide.

References Cited in the .file of this patent UNITED STATES PATENTS2,549,678 'Fiandt Apr. 17, 1951 2,605,703 Lawson Aug. 5, 1952 2,684,030Muskat et al July 20, 1.954 2,692,850 Safranek et a1. Oct. .26, 1954 Q2,694,677 Ostrow Nov. 16, 1954 2,701,234 Wernlund Feb. 1, 1955 2,706,170Marchese Apr. 12, 1 955 2,708,408 Sweetman May 17, 1955 2,732,336 OstrowJan. 24, 1956 2,770,587 Ostrow Nov. 13., 1956 OTHER REFERENCES Articleof Sanrranck et aL, in Platingj January 1948, 91 13919wincnueacncn'enenencn

1. IN A JET PERFORATOR COMPRISING A SHAPED CHARGE MEANS FOR DETONATINGSAID SHAPED CHARGE, A CONTAINER SUBSTANTIALLY SURROUNDING THE SHAPEDCHARGE AND A CAVITY IN THE BASE OF THE SAME, A LINING IN SAID CAVITYCOMPRISING A SUBSTANTIALLY STRAIN-FREE COPPER CONE PRODUCED BY ELEC-